Fault isolation and diagnosis of real-time Internet Protocol (IP) multimedia streams is difficult because the endpoints of the communication have little or no insight into the causes and sources of impairments. The endpoints only know that packets are being lost or delayed by some element, such as a router or switch, along the media network path.
The problem is exacerbated in the case of multicast real-time sessions where any router or switch in the network may replicate and forward packets along different sub-branches of a multicast tree. Hence the impairment patterns seen by different receivers (endpoints) may be very different. Comparing the patterns seen by different receivers may provide further insight into where the problem lies, but is often insufficient to identify with high confidence the particular router, switch, or link causing the fault.
It may be desirable to periodically or continuously monitor many media streams at the same time to get further insight into possible network problems. However the network devices may not have the available processing capacity or bandwidth to continuously send a large number of monitored media streams to one central monitoring site.